1. Field of the Invention
This invention relates to footwear in general, and in particular, to footwear affording enhanced protection against extreme landing impacts acting on the feet of a wearer during certain strenuous athletic activities, such as skateboarding and snowboarding.
2. Description of Related Art
An important function of footwear, particularly athletic shoes, is to protect the wearer's feet against injury caused by forceful contact with the ground or other supporting surfaces. Accordingly, modern athletic footwear typically incorporate some form of a resilient sole disposed below the wearer's foot that serves to attenuate the shock and impact forces imparted to the wearer's feet by the contact surface during running and jumping. This impact attenuation function is typically achieved by the incorporation of resilient, i.e., spring-like, elements within the sole of the shoe, and typically within the mid-sole portion thereof.
These resilient elements typically take the form of a layer of an elastomer, e.g., ethylene vinyl acetate (“EVA”), acting in compression, either alone, or in combination with other forms of springs. Examples of footwear with soles incorporating elastomeric layers acting in combination with various other forms of mechanical springs may be found in, e.g., U.S. Pat. No. 6,212,795 to Nakabe et al.; U.S. Pat. No. 5,918,383 to Chee; U.S. Pat. No. 5,671,552 to Pettibone et al.; U.S. Pat. No. 4,535,553 to Derderian et al.; U.S. Pat. No. 4,342,158 to McMahon et al.; and, U.S. Pat. No. 4,267,648 to Weisz.
Alternatively, the resilient sole elements may incorporate gas-filled springs, such as those described in U.S. Pat. Nos. 5,369,896 and 5,092,060 to Frachey et al.; and, U.S. Pat. Nos. 4,271,606 and 4,183,156 to Rudy.
In addition to elements with resiliency, the soles of modern athletic footwear may also incorporate elements having a relatively high damping characteristic, viz., high viscosity liquids referred to as “gels”. Examples of footwear incorporating liquid gels in the soles thereof may be found in, e.g., U.S. Pat. No. 6,199,302 to Kayano; U.S. Pat. No. 5,718,063 to Yamashita et al.; U.S. Pat. No. 5,704,137 to Dean et al.; U.S. Pat. No. 5,493,792 to Bates; and, U.S. Pat. No. 4,768,295 to Ito.
Although the conventional footwear described in the above references provide some measure of impact protection to the feet of the wearer during athletic activities involving typical running and jumping, they are incapable of providing effective protection during those activities involving extreme shocks and impacts, such as skateboarding and snowboarding, because of their common tendency to “bottom-out,” i.e., to harden rapidly in response to increasingly greater impact forces, such that their ability to store the energy associated with those greater forces is substantially diminished, and a proportionately greater portion of the impact energy is therefore transmitted to the wearer's feet.
A long felt but as yet unsatisfied need therefore exists in the field for footwear that overcomes the bottoming-out problem, and that is capable of protecting the wearer's feet against extreme landing impacts acting thereon during certain strenuous athletic activities.